A well-known application unit according to the class is described for example in DE 44 32 177 A1. Two elongated opposite lip members which between them define a metering gap are disposed on a support beam structure. The liquid or pasty medium to be applied is supplied under pressure to the metering gap via a feed gap via a distribution pipe; this metering gap is designed here as a free-jet nozzle. The medium to be applied leaves the free-jet nozzle metering gap in a free jet, and during so-called direct application this medium then directly strikes against the continuous material web to be coated and which is composed for example of paper, cardboard or a fabric material. In the case of so-called indirect application, the free jet first impacts against the surface of an application roll or another application surface, from which point the medium is transferred to the continuous web within a transfer gap through which the web is guided. At the metering gap outlet, the liquid or pasty medium is also frequently deflected in its direction of movement along a concavely curved deflection surface formed at one of the two lip members, before the medium is then applied in a free jet and at a specific impact angle to the material web or application surface.
To be able to adjust the metering gap width, an adjustment device is provided for at least one of the lip members in the free-jet nozzle application unit explained in DE 44 32 177 A1. In one embodiment version, the lip member to be adjusted is fitted with a thin section which acts as a hinge site. The adjustment device which e.g. comprises a number of adjusting spindles distributed over the lip member's length pivots the lip member around its thin section in order to adjusted the metering gap width in this way. In another embodiment, the lip member to be adjusted is slidably supported so that it can be slid by means of corresponding adjusting spindles toward or away from the facing lip member so as to adjust the gap width in this way. To create a flush transition between the slidable lip member's gap wall surface and feed gap's adjacent gap wall surface in the support beam structure, an elastic connecting strip is provided between the slidable lip member and the support beam. In these known application unit configurations, the gap width can be adjusted to locally varying degrees across the length of the metering gap in order thereby to achieve a profiling of the applied medium on the material web.
Although such known application units can be used to adjust the metering gap width with extreme accuracy, the associated adjustment mechanisms are difficult to design and can only be realized with corresponding costs.